Polyterpenes rubber

Let us consider further the consequences of head-tail additions. If an additional molecule of IPP is added head-to-tail to farnesyl pyrophosphate geranylgeranyl pyrophosphate, a diterpene, is obtained. The series of events outlined above can now be repeated at a higher level of complexity geranylgeranyl pyrophosphate can either be converted to other diter-penes or two molecules of geranylgeranyl pyrophosphate can be joined tail-to-tail to give 40 C bodies. In this way tetraterpenes, i.e. carotenoids, are obtained. Further head-to-tail additions of IPP lead, finally, to the polyterpenes rubber, gutta-percha, and balata. 

Of the polyterpenes rubber, gutta-percha, and balata, our discussion will be restricted to the technically most important product, rubber. About 2,000 species of higher plants produce rubber but only a few of them, mainly from the families Apocynaceae, Asclepiadaceae, Compositae, Euphorbiaceae, and Moraceae, do so in sufficient quantity as to make its extraction technically worthwhile. A few of the more important species are listed in Table 5. The main source of rubber is the rubber tree Hevea brasiliensis. Achras sapota, the chicle of which provides the basic ingredient of chewing gum, is also included in the list. 

Natural rubber displays the phenomenon known as natural tack. When two clean surfaces of masticated rubber (rubber whose molecular weight has been reduced by mechanical shearing) are brought into contact the two surfaces become strongly attached to each other. This is a consequence of interpenetration of molecular ends followed by crystallisation. Amorphous rubbers such as SBR do not exhibit such tack and it is necessary to add tackifiers such as rosin derivatives and polyterpenes. Several other miscellaneous materials such as factice, pine tar, coumarone-indene resins (see Chapter 17) and bitumens (see Chapter 30) are also used as processing aids. 

In this section the rosins and rosin derivative resins, coumarone-indene and hydrocarbon resins, polyterpene resins and phenolic resins will be considered. The manufacture and structural characteristics of natural and synthetic resins will be first considered. In a second part of this section, the characterization and main properties of the resins will be described. Finally, the tackifier function of resins in rubbers will be considered. 

Acyclic C5. The C5 petroleum feed stream consists mainly of isoprene which is used to produce rubber. In a separate stream the linear C5 diolefin, piperylene (trans and cis), is isolated. Piperylene is the primary monomer in what are commonly termed simply C5 resins. Small amounts of other monomers such as isoprene and methyl-2-butene are also present. The latter serves as a chain terminator added to control molecular weight. Polymerization is cationic using Friedel-Crafts chemistry. Because most of the monomers are diolefins, residual backbone unsaturation is present, which can lead to some crosslinking and cyclization. Primarily, however, these are linear acyclic materials. Acyclic C5 resins are sometimes referred to as synthetic polyterpenes , because of their similar polarity. However, the cyclic structures within polyterpenes provide them with better solvency power and thus a broader range of compatibility than acyclic C5s. 

A class of hydrocarbons occurring in many essential oils of plants. They can be regarded as low-molecular weight polymers of isoprene (C5I I8)n. Dipentene is a terpene, while natural rubber, gutta percha and balata have been termed polyterpenes. 

Polyterpenes, coumarone-indene resins, and so-called petroleum resins are produced commercially using cationic polymerization. These are used as additives for rubber, coatings, floor coverings, and adhesives. 

Hydrocarbon resins comprise a range of low-molecular-weight products (M < 3000) used as adhesives, hot-melt coatings, tackifying agents, inks, and additives in rubber. These include products based on monomers derived from petroleum as well as plant sources. The petroleum-derived products include polymers produced from various alkenes, isoprene, piperylene, styrene, a-methylstyrene, vinyltuolene, and dicyclopentadiene. The plant-derived products include polyterpenes obtained by the polymerization of dipentene, limonene,... 

Terpenes are built out of Cs-isoprene units. There is a variety of terpenes ranging from Cs-terpenes which are called hemiterpenes to tetraterpenes with C40 atoms. There are also terpenes with more Cs-units, such as natural rubber, which is a polyterpene. Terpenes are also classified by the number of carbon cycles in the molecule, e.g., monoterpenes can have up to two cyclic systems in one molecule. Examples of some monoterpenes are shown in Scheme 2 myrcene is acyclic,... 

The abovementioned materials can be mixed with one another. A series of other polymers and resins can also be added if the substances listed in 1 to 4 form the bulk of the material. Additional materials are PE, PP, low molecular weight polyolefins, polyterpenes (mixtures of aliphatic and cycloaliphatic hydrocarbons produced by polymerisation of terpene hydrocarbons), polyisobutylene, butyl rubber, dammar gum, glycerine and pentaerythritol esters of rosin acid and their hydration products, polyolefin resins, hydrated polycyclopentadiene resin (substance mixtures manufactured by thermal polymerization of a mixture mainly composed of di-cyclopentadiene with methylcyclopentadiene, isoprene and piperylene which is then hydrogenated). 

Polyterpenes are compounds comprising several hundred isoprene units and give rise to natural rubber. Poly means many, so that rubber is made up of many repeating isoprene units. The name for a compound made up of many such repeating units is a polymer. There are many both naturally occurring and synthetically produced polymers of importance with many applications. 

In addition to terpene s)mthases, the construction of terpenoid carbon skeletons in plants also involves a number of prenyltransferases distinct from those that make the Cio, C15 and C20 diphosphates. One class of prenyltransferases catalyses l -4 condensations of IFF with an FFF or GGFF starter unit to make long-chain polyterpenes, such as rubber, a linear hydrocarbon with cis (Z) double bonds and as many as 30000 isoprene units. The... 

These particles are made from aggregates of 10 to 10 macromolecules of polyisoprene. The presence of the isoprene molecule in the structure of natural rubber makes it part of the polyterpenes family of compounds [1]. 

Balata tree, Mimusops Balata, have achieved economic importance or are considered as resources for natural mbber as a renewable polymer. Chemically, natural rubbers are polyterpenes consisting of 1,4-c -(mbber) or 1,4-frans-(gutta-percha, balata) polyisoprene, generated by enzymatically catalyzed biosynthetic polymerization of isoprene, and stabilized by phospholipids. 

Nevtac . [Neville] Synthetic polyterpene resins tackifier for adhesives, coatings, rubber prods., concrete-curing conqxls., and caulking conq>ds. 

Zonarez . [Arizona] Polyterpene resins thertnofdastic polymers for adhesives, rubber cements, emulsion adhesives, hot melt adhesives/coadt, can sealants, caulking and general sealants., ink, paints, concrete waterproofing agents, varnishes, chewitig and bubble gum bases. 

Common process aids, besides the peptizer, are pine tar, mineral oil, wax, factice, coumarone-indene resins, petroleum resins, rosin derivatives, and polyterpenes. Their main effect is to make rubber soft and... 

Polyterpenes (polyterpenoids). Natural products made up of n C lo units (= 2 n isoprene building blocks) with n>4, the biogenesis of which generally obeys the isoprene rule. The most important P. are the tetra-terpenes (n=4) including carotinoids, ficaprenols, natural rubber, balata, and gutta-percha. The name is also used for hydrocarbon resins (terpene resins) prepared synthetically by polymerization of monoter-penes. 

Isoprenoids with more than eight isoprene units are classified as polyterpenes Natural rubber (caoutchouc), formerly an important raw material for the rubber industry, is primarily obtained by coagulating the milk juice (latex) of Hevea bra-siliensis (Euphorbiaceae) growing in the Amazonian area of Brazil and southeastern Asia. It consists essentially of c -polyisoprene. The milky juice is an emulsion of this polyterpene in water stabilized by proteins as protecting colloids. 

Highly recommended for these polymers PE, PP, PS, ester gums, indene resins, natural rubber, SBR, polyterpene ... 

As the PSA industry evolved, natural rubber (NR) and styrene-butadiene rubber (SBR) were the primary elastomers used. Other backbone polymers were available but were used to a lesser degree. These other elastomers include polychloroprene, butyl rubber and nitrile rubber. Traditionally, formulations containing natural rubber have made use of polyterpene resins as tackifiers, particularly beta-pinene resins. The probable structure of a beta-pinene resin is given as follows and represents the terpene class of resins. 

Fig. 5. Polyken Tack of Natural Rubber Latex Tackified with an Aromatic Modified Polyterpene Resin Emulsion...

The general classifications of resins which are recommended for use as tackifiers for natural rubber latex are polyterpene resins, modified polyterpene resins, modified aromatic hydrocarbons, and all rosin ester dispersions. 

Chromenes, Benzofurans, Benzopyrans, and Precocenes Polyterpenes Biosynthesis Biological Activity Natural Rubber Hevea brasiliensis Guayule Gutta Percha Chicle... 

Balata a rubber-like polyterpene of low molecular mass from the latex of certain tropical trees, in particular from Mimusops balata. The double bonds of B. have trans configuration (see Polyterpenes, Fig.), and it is therefore not very elastic (in contrast to rubber). It softens when heated. 

Caoutchouc elastic, high molecular mass polyter-penes, which can be converted into rubber by vulcanization. Natural C. is a mixture of polyisoprenoids with varying molecular masses, ranging from 300,000 to 700,000. According to X-ray and IR data, the double bonds are cis oriented, whereas in the C.-like polyterpenes, gutta and balata, they are trans. Hundreds of species of plants contain C in their latex, but it can only be obtained on a large scale from a... 

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